1. Field of the Invention
The present invention relates to a vibration-damping resin composition and to a molded article such as a vibration-damping structural component obtained by molding it.
2. Description of the Prior Art
A fiber-reinforced plastic (FRP) using an unsaturated polyester resin has excellent mechanical strength, heat resistance, water resistance, and chemical resistance as well as high productivity and is used in housing appliances such as a bath tub and a washing bowl and in addition in automobile fields as a material for outer plies and cladding components. Recently, an unsaturated polyester sheet molding compound (hereafter, abbreviated as SMC) or a bulk molding compound (hereafter, abbreviated as BMC) has been paid much attention as a plastic material for automobile engine-related components, and has come to be used also for structural components that are required to have high heat resistance and chemical resistance, for example, cylinder head covers, oil pans, etc.
Conventionally, SMC or BMC or the like used for automobile engine-related components have been required of particularly heat resistance and chemical resistance. Recently, vibration-damping properties have been required keenly for the purpose of sound insulation. As a means for imparting vibration-damping properties, there have been proposed a method of decreasing the content of a filler or glass fiber in a molding material, and in addition, a method of adding a block copolymer that imparts vibration-damping properties as described in Japanese Patent Application Laid-open No. 2-102212, and a method of using a resin having a glass transition temperature of 60 to 120.degree. C. as described in Japanese Patent Application Laid-open No. 8-301998.
However, the method of decreasing the content of a filler or glass fiber gives a great influence on the mechanical properties of the construction and finds a limitation in its use. Further, the method of adding a vibration damper such as a block copolymer leads to a decrease in mechanical properties or moldability although it can improve vibration damping properties by increasing the proportion of the vibration damper, so that it is difficult to obtain sufficient vibration-damping properties while ensuring sufficient moldability. Further, in the case of Japanese Patent Application Laid-open No. 8-301998, sufficient vibration-damping properties cannot be obtained particularly in low temperature regions as low as 60.degree. C. or less.